Salinity tolerance of the invasive Pacific oyster (Crassostrea gigas).

Main area:Marine biology
Target group:Biology
Educational level:Bachelor, Masters
Project description:

The invasive Pacific oyster (Crassostrea gigas) settles on hard substrate such as stones or other bivalves. When it settles it cements to the surface and during growth it will cement together with other Pacific oyster forming large oyster reefs. The Pacific oyster is known to tolerate salinities of up to 38 ppt and has an optimal salinity range of 20 – 35 ppt. The oyster tolerates temperatures of -1.8 - 35 °C, but to reproduce it needs water temperatures of 20 °C. Hence, the Pacific oyster owes its invasiveness to a highly plastic physiology, which makes it very tolerant to different environmental conditions. From its arrival in the Danish Wadden Sea it took the Pacific oyster 13 years to form very extensive oyster reefs. In other parts of Danish marine waters the Pacific oyster is known to be present in moderate numbers (e.g., Limfjorden, Randers fjord and Isefjorden). Some very recent observations in my group have shown small specimens of the Pacific oyster to be present in Øresund and off the southern part of Fyn. Therefore the oyster is now known to be present at salinities far below 20 ppt.
The aim of the project is to study the physiology of the Pacific oysters exposed to decreasing salinities in order to identify the lower salinity threshold. Thereby, the border of possible invasions in to the Baltic Sea can be evaluated. The project is done by measurements of the oxygen consumption of resting and not feed oysters (standard metabolic rate, SMR) followed by measurements of the oxygen consumption of oysters feeding at their maximal rate (active metabolic rate, AMR). Also the clearance rate (feeding rate) will be measured and the tissue water content will be used as a proxy for osmotic stress. Based on these measurements it can be evaluated how well the oyster is performing at different salinities.

Methods used:Intermittent respirometry, clearance rate (Coulter counter)
Keywords:Invasive species, Pacific oyster, oxygen consumption, clearance rate, osmotic stress
Supervisor(s):  Bent Vismann